Population research at Johns Hopkins benefits greatly from the facilities provided by the Hopkins Population Center. The list of publications and working papers submitted with this application document a sustained high level of research output in demography and reproductive biology. The Population Center provides a variety of services and facilities which stimulate and advance research activity, bringing together investigators interested in population by providing a first class library and documents center, by supporting computer facilities and software development, by making available a central group for consultation on research design and analysis. Inter-departmental collaboration in reproductive biology is encouraged through support of the Reproductive Biology Council and the Core EM laboratory. A comparable development relative to demographic and social science research is the responsibility of the Demography Council which also oversees the Data Processing Unit and the Mathematical and Statistical Services Unit. Funds are requested for the continuation of support for a Directorate which has responsibility for overall coordination; an Information Unit with capacity for sophisticated information retrieval; a Data Processing Unit which provides remote entry terminals, data management services, software development and guidance in operating in the University's complex computational environment; an EM Laboratory, and a Mathematical and Statistical Services Unit. The Hopkins Center is unique in that it contains two parallel structures: a demographic division and a reproductive biology division. There is frequent interaction between these divisions but essentially each one is self-contained with its own network of investigators. All of the core facilities except the EM laboratory are utilized by both divisions.